Indicator switch



Sept. 1, 1931. c. T. slEEzsl 1,820,990

l INDICATOR SWITCH Filed Apri1-13, 1927 2 sheet's-shee 1 A/4, g ,f Z/ s l' /J wwf/H 4U /m/e/ffa/ /dada Z Ms Sept. 1, 1931.

C. T. SIEBS INDICATOR SWITCH Filed April 13 1927 2 Sheets-'Sheet 2 Patented Sept. l, 1931 UNITED Ns'lnxras lPATENT OFFICE CLAUDE THEODORE SIEBS, 0F CRANFORD, NEW JERSEY, ASSIGNOR T0 WESTERN.

ELECTRIC COMPANY, INCORPORATED, 0F NEW YORK, N. Y., A CORPORATION 0F NEW YORK INDICATOR SWITCH Application led April 13, 1927. Serial No. 183,304.

This invention relates to control systems, and more particularly to improvements in temperature control systems.

Objects of the invention are to provide an improved, simple, and eilicient control system and improved, reliable switching mechanism therefor.

In accordance with the general features of the invention there is provided in one embodiment thereof a system for controlling the temperature of electrically heated furnaces wherein the supply of heating current is controlled in response to predetermined temperature variations within the furnace by a fluid contact switch which is movable aboutva fixed pivot into a plurality of positionsby means of a pair of pivoted members, the movements of Awhich are controlled by a temperature measuring or indicating device actuated by a temperature responslve device mounted within the furnace.

In accordance with a modified form of the invention, a plurality of fluid contact switches are provided for progressively including or excluding portions of a resistance device to decrease .or increase the supply of heat in response to slight temperature variations within the furnace whereby a more uniform temperature is secured.

Other'features and advantages of the invention will become apparent from the following detail description, reference being had to the accompanying drawings, wherein Figs. 1 and 2 are plan and front elevational views, respectively, of a switching mechanism embodying the features of the present invention;

Fig. 3 is a vertical section taken on line 3 3 of Fig. 2;-

Fig. 4 illustrates diagrammatically a temperature control system with which the improved switching mechanism may be employed.

Fig. 5 is a front elevation of a modified form of switching mechanism embodying the invention; o.

Fig. 6 is a side elevation, partly in vsection, of the mechanism shown in' Fig. 5;

Fig.'7 is a fragmentary horizontal section taken on line 7-7 of Fig. 6; y

Fig. 8 is a perspective view of the switch operating levers, the individual levers being separated or disassociated from each other to clearly illustrate lthe construction thereof, and

Fig. 9 illustrates diagrammatically a temperature control system with which the switching mechanism shown in Figs. 5 to 8, inclusive, may be employed Referring now to the drawings and particularly to Fig. 4 thereof, the reference numeral 10 indicates an electrically heated furnace which may be of any desired construction. For the purpose of clearly illustrating the invention, the furnace as shown diagrammatically in the drawings may comprise a cylindrical outer casing 11 within which a smaller cylindrical inner casing 12 is concentrically supported. Encircling the inner casing 12 is an electric heating element 13 to which a supply of heating current is connected to control the temperature within the furnace. Connected in series with the heating element 13 is a iiuid contact switch 14 of 'any well known type comprising a sealed tube 15 housing a pair of electrodes or contact members 16 and 17 and -a body of mercury or other suitable consuitable source of electrical energy (not shown).

The contact switch 14 is supported in a substantially horizontal position and is mounted so that it may be tilted in either direction to allow the conducting fluid 18 to flow into and out of circuit making position to start or discontinue the supply of heating current to'the heating element.- A pair of vertically disposed supporting plates 24 and 25 are secured to each other in spaced relationship by means of bolts 26-26 provided with spacers 27-27 (Fig. 1). The plate 25 is supported by means of -suitable framework7 a portion of which is indicated at 28. Rotatably journaled within the plate 24 is a shaft 30 having a plate 31 secured on the forward end thereof and a cam 32 iixedupon its opposite end. Attached to the plate 31 is a spring claimp 34 which lsupports the contact switch 14 in a substantially horizontal position, as best shown in Fig. 2.

A pair of levers 36 and 37 are pivotally supported intermediate their ends upon pins 38 and 39, respectively, secured to the plate 25. Helical springs 40-40 attached to the .outer ends of these levers serve to normally hold the inner ends thereof downwardly lagainst stops 41-41 scured to the plate 25. The levers 36 and 37 are arranged to engage opposite ends of a straight portion 43 (Fig. 2) formed on the lower side of the cam 32. The construction is such that an upward movement of the inner ends ofthe levers 36 and 37 causes the rotation of the cam 32 in a clockwise and counter-clockwise direction, respectively. It will be understood that such rotation of the cam 32 causes the tilting of the contact switch 14 into a plurality of positions to start or discontinue the supply of heating current to the heating element 13.

The means for imparting movement to the levers 36 and 37 to open or close the contact switch 14 in response to predetermined temperature variations within the furnace will now be described. Slidably mounted in a bracket 45 secured to the frame 28 is a slide 46 which is continuously reciproc ated by a cam 47 secured to a horizontally disposed shaft 48 driven from any suitable source of power not shown).' The cam -47 engagesone end of a lever 50 which is pivoted intermediate its ends upon a pin 51 secured to the frame 28. The opposite end of the lever 50 engages the lower end of the slide 46. The slide 46 returns by gravity to its lowermost position as .the operating lever 50 approaches its lowest position .of travel,

the weight of the slide being sufhcient to constantly hold the lever in contact with the cam V47. Arranged so as to be free to travel between the upper edge of the slide 46 and the lower edges of the levers 36 and 37 is a pointer 54 of a measuring or indicating instrument, such as galvanometer 55 which may be connected in the usual potentiometer circuit. As shownin Fig..4, the galvanometer 55 is connected in series with a temperature responsive device, such as a thermo-couple 56 mounted within the furnace. One end of the galvanometer coil is connected to a resistance 57 by a conductor 58 and the other end of the galvanometer coil is connected to one terminal of the thermocouple 56 by a conductor 60. The other terminal of the thermocouple is connected by means of a conductor 6l to a movable Contact 62 which bears upon the resistance 57. The resistance 57 is connected in series with an adjustable resistance 64 and a battery or source of direct current 65.

Associated with theJ movable contact 62 is a pointer 66 which cooperates with a suitably calibrated scale 67 associated with the resistance 57 to indicate the temperature I-f, upon starting the operation of.

the system Vby closing the switch 22, the temperature within the furnace is below the desired predetermined value, the galvanometer pointer 54 will be defiected to the left from its balanced position, as shown in Fig. 2. When in this position, the pointer 54 is disposed between the lower edge of the lever 36 and the upper edge of the slide 46, thus causing the lever 36 to be moved upwardly beyond the lever 37 during the upward movement of the slide 46, whereby the cam 32 is rotated in a clockwise direction, causing the contact switch 14 to be tilted to its closed position as shown in the drawings. As the temperature within the furnace approaches the desired predetermined value, .the pointer 54 moves toward the right (Fig. 2) to its balanced or neutral position and when in this position -the galvanometer pointer is disposed in the space provided therefore between the adjacent ends of the levers 36 and 37. When the temperature within the furnace increases above the desired predetermined value, the pointer 54 is deflected to the right beyond the balanced i or neutral position within itis disposed between the upper edge of the slide 46 and the lower edge of the lever 37, and during the next upward movement of the slide 46, the lever 37 is movedupwardly beyond the lever 36 causing the cam 32 to rotate in a counterclockwise direction, thereby tilting the contact switch into its open position, thus discontinuing the supply of heating current to the heating element 13.

In accordance with a modified form of the invention, a mechanism for operating a plurality of fluid contact switches to decrease or increase the amount of heat supplied to an electrically heated furnace in response to enig -to predetermined temperature `variations is `shown in Figs. 5 to 8, inclusive. The reference numeral indicates a portion of a supporting frame to which an L-shaped bracket 7 lis rigidly secured. Supported at one end by the frame 70 and at its opposite end by the bracket 71 is a horizontally disposed shaft 72 which carries a pair of rotatable blocks 74 and 75. A pair of fluid contact switches 76 and 77 are 'supported in a substantially horizontal position within spring clampingmembers 78 and 79 secured to the blocks 74 and 75, respectively. The switches 76 and 77 are'suitably spaced upon the shaft 72 by means of tubular spacing members 80 and 81 (Fig. 6).

The contact switches 76 and 77 are similar to the contact'switch 14, hereinbefore described. As shown in Fig. 9,.one terminal of the switch 77 is connected to one end of the heating element 13 by a conductor 83 and the corresponding terminal of the switch 76 is connected to an intermediate point 84 of the heatin element. The opposite terminals of eac of the switches are connected to the source of current through the switch 22. It is obvious that more heat is supplied to the furnace when the switch 76 is closed and the switch 77 is open than with the switch 77 closed and the switch 76 open, since under the former conditions, the electrical current passes through only a portion of the heating element while under the latter conditions the current passes through the whole heating element.

The means for selectively operating the contact switches 76 and 77 in response to predetermined temperature variations will now be described. Pivotally mounted intermediate its ends upon a horizontally disl. posed pin 86 supported by the frame 70 and the bracket 71 is a U-shaped lever 87 and similarly mounted upon a horizontally di'sposed in 88 are a pair of U-shaped levers 90 an 91. Elongated slots or apertures' 93-93 formed in the inner end portions of the levers 87, 90 and 91 engage horizontally disposed pins 94-94 supported by the frame 70 and the bracket 71. Helical tension springs 95-95 attached to the outer-ends of the levers serve to normally urge the inner or adjacent ends thereof downwardly, which movement is limited by the upper edges of the slots 93 engaging the pins 94.

. Secured to the blocks 74 and 75 on either side of the shaft 72 are a plurality of pins 97-e-97. Fingers 98 and 99 extending upwardly from the inner end of the lever' 87 are provided with pointed projections 100 and 10.1, respectively, (Fig. 8). The projection i90 of the finger 98 is positioned to engage a pin 97 secured to the block 74 on the letti; side of the shaft 72 (Fig. 5), and the project-ion 101 of the finger 99 is positioned a pin 97 secured to the block 75 on the right side of the shaft 72. Fingers 102 and 103 extending upwardly from the inner end of the leverl 90 are provided with pointed projections 104 and 105, respectively. The projection 101 is positioned to engage a pin 97 secured to the block 74; on the right side ot the shaft 72 (Fig. 5), and the projection 105 is positioned to engage a pin 97 secured to the block 75 on the left side of the shaft 72. The lever 91 is also provided with upwardly extending fingers 106 and 107 having pointed projections 108 and 109, respectively, which are positioned to engage the pins 97 secured to the blocks 74 and 75,

,respectively, on the right side of the shaft From the construction above described, it is obvious that when the inner end of the lever 87 is moved upwardly, the contact switch 76 is tilted in a clockwise direction to its closed position and the switch 77 is tilted in a counter-clockwise direction to its open position. Also. when the inner end of the lever 90 is moved upwardly, .the switch l76 is tilted in a counter-clockwise direction to its open position, and the switch 77 is tilted in a clockwise direction to its closed position. Furthermore, when the inner end of the lever 91 is moved upwardly, it is apparent that both the switches 76 and 77 are tilted in a connter-clm-kwise direction to their open positions. The means for actuating the levers 87. 90 and 91 to control the operation of the switches 76 and 77 Will next be described.

Pivotally supported upon pins 111-111 secured to opposite sides of the frame 70 is a horizontally disposed U-shaped carriage or lever 112 which is disposed immediately below the levers 87. 90 and 91. A reciprocatory movement is imparted to the carriage 112 by a continuously rotating cam 114 secured to a horizontally disposed shaft 115 driven from any suitable source of power (not shown). The cam 114 engages a roller 116 carried upon the lower end of an arm 117 which is secured to the carriage 112.

In the operation of the above described mechanism, the. pointer 54 of the galvanolneter 55 is arranged so as to he free to travel between levers87, 90 and 91. and the upper surface of a horizontally disposed angle iron 119 secured to the carriage 112. lVhen the temperature decreases below the desired predetermined value, the galvanometer pointer is deflected tothe left 5) wherein it is disposed' between the angle iron 119 and the lever 87 in such manner that the upward movement ot thc carriage 112 causes the inner portion of the lever 87 to move unwardly. thus tilting the switch 76 in a clockwise direction to its closed position and at the same time tilting the switch 77 in a counter-clockwise direction to its open position whereby the maximum amount of heat is supplied to the furnace. As the temperature approaches the desired predetermined value, the galvanome'ter pointer moves toward the right to its balanced or neutral position and when in this position the galvanomcter pointer is disposed between the angle iron 119 and the lever 90 in such manner that the upward movement of the carriage 112 causes the inner portion of the lever 90 to move upwardly, thus opening the switch 7G and closing the switch 77, whereby the supply of heat is decreased since the current now passes through the whole heating element. lVhen the temperature increases above the desired predetermined value, the galvanometer pointer is deflected to the right beyond its balanced or neutral position wherein it is disposed between the angle iron 119 and the lever 91 in such manner that the upward movement of the carriage 112 causes the inner portion of the lever 91 to move up- `wardly, thus opening both of the switches 7G and 77, whereby the. supply of heating current is discontinued. The lever 90 is slotted as indicated at 120 (Fig. 8) to prevent its movementupwardly during the upward movement of the lever 91.

From the above description it will be understood that the improved control system and switching mechanism renders it possible to constantly maintain a uniform temperature within electrically heated furnaces particularly of the muftle or similar types. It. is obvious, of course. that the novel features of the invention are capable of other applications within the scope of the appended claims. 'l

What is claimed is:

1. In an electrical control system, a circuit controlling mechanism comprising a fluid contact switch rotatable about a iixed pivot into a plurality of circuit controlling positions, a reciprocating carriage. a pivoted member actuated by the carriage for rotating the switch into one-ot said positions, and a second pivoted member actuated by y the carriage for rotating the switch into an'- other of said positions.

2. In an electrical control system, a circuit controlling mechanism comprising a fluid contact switch rotatable about a fixed pivot into a plurality of circuit controlling positions, an indicating device, means responsive to the indicating device for rotating the contact switch into one of said positions, and means also responsive to the indicating device for rotating the contact switch into another of said positions.

3. In an electrical temperature control system, a circuit controlling mechanism comprising a Huid contact switch pivotally movable into a plurality of circuit controlling positions, a reciprocating carriage, a temperature indicating device, and a pair of pivoted members disposed on opposite sides of the pivotal axis of the switch and selectively actuated by the carriage in response to the indicating device 'for selectively moving the Contact switch into said positions.

4. In an electrical control system, a circuit controlling mechanismI comprising a plurality of fluid contact switches rotatable about acommon pivotal axis into a plurality of circuit controlling positions, a plurality of pivoted members if( r actuating the switches, a reciprocating member for actuating the pivoted members, and means including an element responsive to variations in a condition for selectively rendering lthe pivoted members effective to selectively rotate the switches into certain of said positions.

5. In an electrical control system, a circuit controlling mechanism comprising a liuid Contact switch pivotally movable into a plurality of circuit controlling positions and having a plurality of circuit controlling contacts, an actuating member for engaging the switch on one side of its pivotal axis to close the contacts, a second actuating member for engaging the switch on the opposite side oi its pivotal axis to open the contacts, and means responsive to a predetermined condition for selectively rendering the switch actuating members etfective.

In witness whereof, I hereunto subscribe my name this 21st day of March, A. D.,

CLAUDE THEODORE SIEBS. 

